1. Field of the Invention
The present invention is directed to a medical apparatus of the type having a data processing device for storing an image dataset of the body of a living subject, having a medical instrument for introduction into the body of the subject, and a navigation system for determining the position of the medical instrument relative to the body of the subject.
2. Description of the Prior Art
A medical apparatus of this type is disclosed in German OS 199 51 501. For example, the image dataset—which is specifically a three-dimensional image dataset—of the region of interest of the body of a patient is produced with an X-ray device. A surgeon introduces the medical instrument into the body of the patient, particularly, in a minimally invasive procedure. A position sensor of the navigation system is arranged at the medical instrument, so that the navigation system identifies the position, i.e. the location and orientation, of the medical instrument relative to the body of the patient. An image of the medical instrument can be subsequently mixed into the image represented by the image dataset on the basis of the position determination, i.e. on the basis of a determination of the position coordinates of the medical instrument. The image can be presented, for example, on a monitor.
The image dataset can be pre-operatively produced, for example with a computed tomography apparatus. For mixing in the image of the medical instrument it is necessary to undertake a spatial transformation of the coordinates (with respect to a first coordinate system) of the position sensor of the navigation system arranged in a defined way at the medical instrument into the spatial coordinates of the image of the patient acquired with the computed tomography apparatus and employed for the navigation. This transformation is referred to as registration. Markers can be attached to the patient for the registration. The positions of the markers are identified in the first coordinate system, with the position sensor of the navigation system and are identified (for example, by manual entry with an input device) in the coordinate system of the image stored in the data processing device, which was acquired with the computed tomography apparatus and is employed for navigation. Ultimately, a transformation can be calculated from the two points sets of the markers identified in the first coordinate system and in the coordinate system of the image employed for navigation. The transformation transforms the positions of the medical instrument, acquired in the first coordinate system with the position sensor of the navigation system, into the coordinates of the image during the navigation.
If the image dataset of the body of the patient is intra-operatively produced, for example with an X-ray device as likewise disclosed in German OS 199 51 502, then the navigation system can be implemented such that, in addition to determining the position of the medical instrument, ii also determines the position of the X-ray device, so that a registration for mixing the image of the medical instrument into the image of the body of the patient can be omitted.
Bone fragments that arise, for example, in the case of splinter fractures can be set with a minimally invasive procedure. The bone fragments are grasped with a medical instrument introduced into the body of the patient and are subsequently set. Medical instruments suitable for setting bone fragments are described and shown, for example, in Irmengard Middelanis, Marget Liehn, Lutz Steinmüller, Rüdiger Döhler (Editors), OP-Handbuch, Grundlagen Instrumentation OP-Ablauf, Springer Verlag, Berlin, Heidelberg 1995, pages 159 and 160. The movement of the medical instrument during the intervention can be tracked with the known and above-described medical devices by mixing the image of the medical instrument into the image of the body of the patient. However, a visualization of the position of the bone fragments modified as a result of the setting is not possible with such a known system.
German OS 100 57 023 discloses providing an imaged bone fragment with a marking in a volume dataset formed by a series of 2D projections of a bone fracture acquired from different projection directions. For assisting the physician treating the bone fracture, the marking is subsequently mixed into at least one of the 2D projections.